Derotation apparatus for treating spinal irregularities

ABSTRACT

Treatment of spinal irregularities, including, in one or more embodiments, derotation apparatus and systems that can be used to reduce the rotation of vertebral bodies. Derotation apparatus that may comprise a tube assembly comprising an inner sleeve and an outer sleeve disposed over the inner sleeve. The inner sleeve may have a distal end for attachment to an implant. The tube assembly may further comprise a handle assembly. The tube assembly may further comprise a ball joint assembly disposed between the tube assembly and the handle assembly. The ball joint assembly may comprise a ball joint configured for attachment to a coupling rod. The ball joint assembly further may comprise a reducing extension below the ball joint, the reducing extension being sized to fit in a central bore of the inner sleeve. Orthopedic fixation devices comprising a ball joint are also disclosed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/643,537, filed on Mar. 10, 2015, which is a divisional of U.S. patentapplication Ser. No. 13/275,499, filed on Oct. 18, 2011, now U.S. Pat.No. 9,005,204, which is a continuation-in-part of U.S. patentapplication Ser. No. 12/632,445, filed on Dec. 7, 2009, now U.S. Pat.No. 8,475,467, the entire disclosures of which are incorporated hereinby reference in their entities for all purposes.

FIELD OF THE INVENTION

The present disclosure generally relates to treatment of spinalirregularities. In particular, in one or more embodiments, the presentdisclosure relates to derotation apparatus and systems that can be usedto reduce the rotation of vertebral bodies

BACKGROUND

Many types of spinal irregularities can cause pain, limit range ofmotion, or injure the nervous system within the spinal column. Theseirregularities can result from, without limitation, trauma, tumor, discdegeneration, and disease. By way of example, scoliosis and kyphosis areirregularities that can result in a complex, three-dimensional problemwith lateral curvature of the spine and segmental vertebral rotation.Advances in medicine and engineering have provided doctors with aplurality of devices and techniques for correcting these deformities orirregularities.

One technique for treating scoliosis is the Harrington rod. TheHarrington rod operates on a distraction system attached by hooks to thespine that when distracted, straightens the curve in the spine. Untilthe 1970's, the Harrington rod was the preferred method of treatment forscoliosis. Follow-up studies of these rods documented the negativeeffects of using distraction rods alone for correction of spinaldeformities, including “flat back syndrome” and the resultingdegenerative changes in the lower lumbar spine. Other methods ofmanagement, including spinal fixations systems that include segmentalwires, hooks, rods and/or bone fasteners (e.g., pedicle screws) haverevolutionized the treatment of spinal deformities. The advent andavailability of smaller and stronger bone fasteners has further advancedtreatment, allowing for effective application of corrective forces toposterior systems into the high thoracic spine.

Until recently, spinal fixation systems comprising bone fasteners androds were used almost exclusively to correct the lateral curvature ofthe spine, with little attention paid to segmental vertebral derotation,primarily because bone fastener instrumentation did not provide a meansof rotating the individual vertebral bodies. These systems focused onreducing the rod into the bone fasteners and using rod grips and/or insitu benders to translate the rod to restore sagittal and coronal planebalance. While these patients appear to be corrected on an A-P orlateral x-ray, they frequently present with pronounced rib hump, oraxial twisting of the spine, which can result in significant pulmonarycompromise and further degenerative changes in the spine.

Techniques have also been developed to address segmental vertebralrotation caused by irregularities, such as scoliosis. For instance,derotation systems have been used for the treatment of segmentalvertebral rotation. Current derotation systems typically include a tubeor series of tubes that slot over the implant (e.g., pedicle screw) muchlike a counter torque. These tubes allow the surgeon to push on androtate the vertebral bodies away from the instrumentation, which whenapplied to the apex of the deformity, will straighten the lateralcurvature and can reduce some of the individual rotation between bodies.However, this maneuver frequently results in flat back syndrome and,more importantly, very high applied forces to individual screws, whichcan lead to bone fasteners breaching the medial or lateral walls of thepedicle. This leads to loss of fixation at these levels and can resultin paralysis if the breached screws impact the spinal cord. To reducethe force applied to any one screw, derotation systems may link multiplescrews together so that the force of correction is applied over multiplescrews. However, the surgeon typically cannot connect more than twotubes, and the process to connect the tubes is time consuming,confusing, and often requires separate instruments to assemble andtighten the system together. These factors in an already long andcomplex deformity case have limited the impact of derotation systems forposterior spinal fusion procedures.

Thus, there is a need for improved derotation systems that can securelyconnect to implants with efficient coupling to multiple implants.

SUMMARY

An embodiment of the present invention includes a derotation apparatus.The derotation apparatus may comprise a tube assembly comprising aninner sleeve and an outer sleeve disposed over the inner sleeve. Theinner sleeve may have a distal end for attachment to an implant. Thetube assembly may further comprise a handle assembly. The tube assemblymay further comprise a ball joint assembly disposed between the tubeassembly and the handle assembly. The ball joint assembly may comprise aball joint configured for attachment to a coupling rod. The ball jointassembly further may comprise a reducing extension below the ball joint,the reducing extension being sized to fit in a central bore of the innersleeve.

The features and advantages of the present invention will be readilyapparent to those skilled in the art. While numerous changes may be madeby those skilled in the art, such changes are within the spirit of theinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a derotation apparatus in accordance with oneembodiment of the present invention.

FIG. 2 illustrates an exploded view of a derotation apparatus inaccordance with one embodiment of the present invention.

FIG. 3 illustrates an embodiment of a tube assembly of a derotationapparatus.

FIG. 4 illustrates an embodiment of a derotation apparatus with a tubeassembly in an unlocked position.

FIG. 5 illustrates an embodiment of a derotation apparatus with a tubeassembly in a locked position in accordance with one embodiment of thepresent invention.

FIG. 6 illustrates an embodiment of a derotation apparatus with the balljoints at different rotational angles.

FIG. 7 illustrates an embodiment of a derotation apparatus with one ofthe ball joints oriented at an angled with respect to the derotationapparatus.

FIG. 8 illustrates an exploded front view of a ball joint in accordancewith one embodiment of the present invention.

FIG. 9 illustrates an exploded side view of a ball joint in accordancewith one embodiment of the present invention.

FIG. 10 illustrates an embodiment of a ball joint in an unlockedposition in accordance with one embodiment of the present invention.

FIG. 11 illustrates an embodiment of a ball joint in a locked positionin accordance with one embodiment of the present invention.

FIG. 12 illustrates an embodiment of a coupled derotation system withtwo derotation apparatuses attached on either side of the same vertebralbody.

FIG. 13 illustrates an embodiment of a coupled derotation system withthree derotation apparatuses in an inline arrangement.

FIG. 14 illustrates an embodiment of a coupled derotation system withmultiple derotation apparatuses.

FIG. 15 illustrates a derotation apparatus in accordance withalternative embodiments of the present invention.

FIG. 16 illustrates an embodiment of a tube assembly of the derotationapparatus of FIG. 15.

FIG. 17 illustrates an end view of the tube assembly of FIG. 16 inaccordance with one embodiment of the present invention.

FIG. 18 illustrates an embodiment of a ball joint assembly with a handleassembly disposed at one end of the ball joint assembly, the ball jointassembly having a reducing extension.

FIG. 19 illustrates an orthopedic fixation device in accordance with oneembodiment of the present invention.

FIG. 20 illustrates coupling of a ball joint of the orthopedic fixationdevice of FIG. 19 to a rod in accordance with one embodiment of thepresent invention.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

FIGS. 1 and 2 illustrate a derotation apparatus 10 in accordance with anembodiment of the present invention. As illustrated, derotationapparatus 10 comprises a tube assembly 20, a ball joint assembly 30, anda handle assembly 40. Tube assembly 20 may comprise an inner sleeve 50and an outer sleeve 60 disposed over inner sleeve 50 with inner sleeve50 having a distal end 70 configured and adapted for attachment to animplant (not illustrated). In an embodiment, the implant may be attachedto a vertebral body. Ball joint assembly 30 may comprise at least oneball joint 80. As illustrated, ball joint assembly 30 comprises two balljoints 80. As will be discussed in more detail below, force may beapplied to handle assembly 40 to derotate the vertebral body to whichthe implant is attached. This should result in reducing the rotationbetween vertebral bodies in a patient's spine. In addition, rotation ofthe vertebral bodies may also straighten curvature of the spine.

Referring now to FIGS. 1-5, tube assembly 20 of derotation apparatus 10will be described in more detail in accordance with one embodiment ofthe present invention. FIG. 3 illustrates tube assembly 20 with balljoint assembly 30 and handle assembly 40 removed. In general, tubeassembly 20 should attach derotation apparatus 10 to the implant (notillustrated). As previously mentioned, tube assembly 20 includes innersleeve 50 and outer sleeve 60 disposed over inner sleeve 50.

Inner sleeve 50 includes distal end 70 configured and adapted forattachment to an implant (not illustrated). In an embodiment (notillustrated), distal end 70 fits over at least a portion of an implant.While not illustrated, the inner surfaces of distal end 70 may includefeatures configured and adapted for attachment to the implant. Forexample, distal end 70 may include a connection that allows for couplingthe inner sleeve 50 to the implant by applying some force. For example,the distal end 70 may be flexible so that the distal end 70 can fit overa head of the implant when longitudinal force is applied to the innersleeve 50. In another embodiment, a dovetail-type connection may beincluded, such that placement of distal end 70 over the implant withrotation should couple the inner sleeve 50 to the implant, thuspreventing separation. Other suitable mechanisms may be used to preventseparation of distal end 70 from the implant. The implant may includeany of a variety of surgical implants that may be secured to a vertebralbody, including, for example, a spine stabilization system that includesa bone fastener (e.g., a pedicle screw) coupled to a rod. By way ofexample, distal end 70 may fit over the head of the bone fastener.Distal end 70 may include slots 90 through which the rod extends whendistal end 70 is fitted over the bone fastener, for example. Distal end70 may further include a beveled surface 100.

Inner sleeve 50 may further include locking mechanisms 110 that extendradially from inner sleeve 50 opposite distal end 70. Locking mechanisms110 may each include a stop 120, actuator 130, and guide 140. Asillustrated, the stop 120 and actuator 130 may be on either end of theguide 140 with the guide 140, for example, being a pin or rod extendingbetween stop 120 and actuator 130. Pressing down on actuator 130 shouldcause locking mechanisms 110 to depress towards inner sleeve 50.

Referring now to FIGS. 1-5, outer sleeve 60 will be described in moredetail in accordance with one embodiment of the present invention. Aspreviously mentioned, outer sleeve 60 may be disposed over inner sleeve50. Outer sleeve 60 may comprise a first opening 150 and a secondopening 160 connected by channel 170. While not illustrated, outersleeve 60 further may comprise corresponding openings to first opening150, second opening 160, and channel 170, on the opposite side of outersleeve. First opening 150 and second opening 160 should each have agreater width than channel 170. Second opening 160 should be closer toproximal end 175 of outer sleeve 60 than first opening 150. Channel 170should generally be dimensioned to allow passage of guide 140 of lockingmechanisms 110, but should not be of sufficient size for passage of stop120, when tube assembly 20 is assembled. First opening 150 and secondopening 160 should be dimensioned to allow penetration of stop 120.Outer sleeve 60 further may comprise additional openings, such as thirdopening 180 and fourth opening 190. These additional openings shouldprovide access to inner sleeve 50 after assembly of tube assembly 20,for example, so that interior components of tube assembly 20 may beinspected and/or cleaned as desired. In an embodiment, outer sleevefurther comprises a chamfered distal end 210.

As illustrated by FIGS. 2 and 3, shaft 200 may be coupled to outersleeve 60 in accordance with one embodiment of the present invention. Ingeneral, shaft 200 may extend axially from proximal end 175 of outersleeve 60. In an embodiment, shaft 200 and outer sleeve 60 may be aunitary piece. In an alternative embodiment (not illustrated), shaft 200may be attached to outer sleeve by any suitable mechanism, such as by abolted and/or threaded connection. As illustrated, shaft may have asquare-shaped proximal end 430. While proximal end 430 of shaft 200 isillustrated as generally square in shape other shapes (e.g., circular)may also be suitable in accordance with embodiments of the presentinvention.

FIGS. 4 and 5 illustrate operation of the locking mechanisms 110 of tubeassembly 20 in accordance with one embodiment of the present invention.As will be described below, locking mechanisms 110 may be used to couplederotation apparatus 10 to the implant (not illustrated). The followingdescription is with respect to movement of one of locking mechanisms 110from an unlocked to a locked position. However, it should be understoodthat the illustrated embodiment contains two locking mechanisms 110 withboth locking mechanisms 110 functioning in a similar manner toeffectuate locking and unlocking of tube assembly 20.

FIG. 4 illustrates tube assembly 20 with locking mechanism 110 in anunlocked position in accordance with one embodiment of the presentinvention. As illustrated, when tube assembly 20 is unlocked, outersleeve 60 may be disposed over inner sleeve 50 with distal end 70 ofinner sleeve 50 uncovered. In an embodiment, when unlocked, lockingmechanism 110 should extend through first opening 150 in outer sleeve60. Block 120 may be positioned in first opening 150 so that lockingmechanism 110 is engaged with first opening 150, preventing movement oflocking mechanism 110. This should fix the position of inner sleeve 50with respect to outer sleeve 60. When in the unlocked position, distalend 70 of inner sleeve 50 may be placed over at least a portion of animplant (not illustrated). Various mechanisms may be applied so that thederotation apparatus 10 is prevented from separating from the distal end70 of the implant.

FIG. 5 illustrates tube assembly 20 with locking mechanism 110 in alocked position in accordance with one embodiment of the presentinvention. The tube assembly 20 may be placed in the locked position tofurther secure the inner sleeve 50 onto the implant. To place thelocking mechanism 110 in a locked position in accordance with oneembodiment, actuator 130 should be pressed causing locking mechanism 110to depress towards inner sleeve 50. Stop 120 may move completely throughfirst opening 150 so that stop 120 disengages with first opening 150.With locking mechanism 110 depressed, pressure should be applied to tubeassembly 20 forcing outer sleeve 60 further down onto inner sleeve 50.As outer sleeve 60 passes down onto inner sleeve 50, guide 140 shouldpass through channel 170 until locking mechanism 110 reaches secondopening 160. Actuator 130 should then be released so that lockingmechanism 110 raises and engages with second opening 160 with stop 120preventing movement. As outer sleeve 60 is forced down onto first sleeve50, chamfered distal end 210 of outer sleeve 60 passes over beveledsurface 100. This forces the outer sleeve 60 against distal end 70 ofinner sleeve 50 pressing distal end 70 tighter against the implant (notillustrated). This tightening force should clamp distal end 70 onto theimplant preventing separation of distal end 70 from the implant.Accordingly, in this manner, derotation apparatus 10 can be securelyconnected to an implant. Other suitable mechanisms for securingderotation apparatus 10 onto an implant may also be used in accordancewith embodiments of the present invention.

Derotation apparatus 10 may further comprise ball joint assembly 30. Ingeneral, ball joint assembly 30 should be configured and adapted tocouple derotation apparatus 10 to least one additional derotationapparatus 10. As discussed below with respect to FIGS. 12-14, two ormore derotation apparatuses 10 may be linked by at least one couplingrod 220 forming a coupled derotation system 225. Referring now to FIGS.1 and 2, ball joint assembly 30 may comprise at least one ball joint 80.In an embodiment, at least one ball joint 80 may be a spring-loaded balljoint. In general, each of at least one ball joint 80 may be rotatable.For example, each of at least one ball joint 80 should be rotatableabout at least one axis and, preferably, at least two axes. In anembodiment illustrated by FIG. 6, each of at least one ball joint 80 maybe rotated about z-axis 230. For example, at least one ball joint 80 mayrotate about z-axis 230 by an angle of up to about 360°. As illustrated,the two ball joints 80 may have an angle of rotation of about 90° withrespect to one another. In an embodiment illustrated by FIG. 7, at leastone ball joint 80 may be rotated about a y-axis (not illustrated), whichwould extend in a direction perpendicular to the figure. For example, atleast one ball joint 80 may rotate about the y-axis by an angle (θ) ofup to about 360°. As illustrated, one of the ball joints 80 may rotateabout the y-axis by an angle (θ) of at least about 20°.

Referring now to FIGS. 2, 8 and 9, ball joint assembly 30 will bedescribed in more detail with respect to one embodiment of the presentinvention. As illustrated, ball joint assembly 30 comprises at least oneball joint 80. Each ball joint 80 may comprise a ball 240 containedwithin a housing 250 with ball 240 and housing 250 disposed on shaft200. In an embodiment, ball 240 is formed by upper portion 260 and lowerportion 270 that when matched together form ball 240. Upper portion 260and lower portion 270 may each be generally annularly shaped so thateach portion can fit onto shaft 200. As illustrated, upper portion 260may be a separate piece that forms the top half of ball 240 while lowerportion 270 may be a separate piece that forms the lower half of ball240. In an embodiment (not illustrated), upper portion 260 and lowerportion 270 are unitary pieces or, alternatively, coupled in somemanner. Each of upper portion 260 and lower portion 270 may comprise ahole, such as tapered through hole 275 to, for example, facilitaterotation of at least one ball joint 80 on shaft 200. In an embodiment,upper portion 260 and lower portion 270 of each ball joint 80 maycomprise serrated ball edges 285 on at least a portion of theirrespective exterior surfaces forming the outer surface of respectiveball 240.

In the illustrated embodiment, each of upper portion 260 and lowerportion 270 comprises a tab, for example, upper tab 280 and lower tab290. Upper tab 280 and lower tab 290 may extend radially and outwardlyfrom upper portion 260 and lower portion 270, respectively. Together theupper tab 280 and lower tab 290 may be configured and adapted to form aclamp 300 that grips coupling rod 220 (illustrated on FIGS. 12-14). Inthis manner, each ball joint 80 may retain a corresponding coupling rod220. In an embodiment, clamp 300 formed by upper tab 280 and lower tab290 is open, for example, to facilitate insertion of coupling rod 220.In an embodiment, clamp 300 is generally u-shaped. As illustrated, thefacing surfaces 310 of upper tab 280 and lower tab 290 may be rounded sothat upper tab 280 and lower tab 290 form rod opening 315 for receivingcoupling rod 220.

As illustrated by FIGS. 2, 8, and 9, each one ball joint 80 further maycomprise inner washers 320 and outer washers 330 that are each disposedover shaft 200, in accordance with one embodiment of the presentinvention. Inner washers 320 and outer washers 330 may each comprise acentral opening (not illustrated) that is dimensioned for shaft 200 tofit through. Inner washers 320 may each comprise a protruding rim 340with a rounded surface 350. In an embodiment, rounded surface 350 may besmooth to allow for rotation of ball 240. Inner washers 320 also mayeach comprise an outer shoulder 360. As illustrated, outer shoulder 360of each of inner washers 320 may be inwardly facing, in that outershoulder 360 may face ball 240 of the respective ball joint 80. Innerwashers 320 further may each comprise an inner spring shoulder 370facing in the opposite direction of outer shoulder 360. Outer washers330 may each comprise an inner shoulder 380. This inner shoulder 380 isoutwardly facing because it faces away from ball 240. In an embodiment,one or more of outer washers 330 may be integral with housing 250. Asillustrated by FIG. 8, this integral washer of outer washers 330 may bethe uppermost of outer washers 330, in accordance with one embodiment.In an alternative embodiment (not illustrated), each of outer washers330 may be separate pieces from housing 250. As illustrated by FIG. 9,the lowermost of outer washers 330 may be separate from housing 250 inaccordance with one embodiment. In an embodiment, one or more of outerwashers 330 may each comprise one or more serrated edges. In theillustrated embodiment, each of outer washers 330 may comprise innerserrated edge 390 and outer serrated edge 400. As illustrated, innerserrated edge 390 may be rounded for mating with ball 240.

Each ball joint 80 may further comprise springs 405. As illustrated,springs 405 may be disposed over shaft 200 on either side of innerwashers 320. In an embodiment, springs 405 are compression springs. Inan embodiment, each ball joint 80 may share one of springs 405. In theillustrated embodiment, each ball joint 80 comprises two springs 80 witheach ball joint sharing one of springs 80. In an alternative embodiment(not illustrated), each of at least one ball joint 80 may comprise onecompression spring.

Referring now to FIGS. 1 and 2, handle assembly 40 will be described inmore detail, in accordance with one embodiment of the present invention.In the illustrated embodiment, handle assembly 40 comprises handle 410and cap 420. Handle 410 may be generally tubular in shape with apassageway extending longitudinally therethrough. As illustrated, handle410 may comprise lower tubular section 440 and upper tubular section450. In an embodiment, lower tubular section 440 may have an innerdiameter that is smaller than the inner diameter of upper tubularsection 450. In an embodiment (not illustrated), lower tubular section440 may have inner threads. When derotation apparatus 10 is assembled,shaft 200 may be received into lower tubular section 440. One or moreholes 460 may be formed in upper tubular section 440. Handle 410 furthermay comprise inner cap shoulder 470, for example, at the intersection oflower tubular section 440 and upper tubular section 450. As illustrated,interior cap shoulder 470 may be upwardly facing.

In an embodiment, cap 420 may be configured and adapted to lock handle410 on derotation apparatus 10. As illustrated, cap 420 may comprisehead 480, elongated shaft 490, and exterior threads 500. When derotationapparatus 10 is assembled, for example, cap 420 may be disposed in theinterior of handle 410 with cap 420 engaging inner cap shoulder 470 ofhandle 410 and elongated shaft 490 extending down into lower tubularsection 440. While not illustrated, cap 420 may include features to lockinto handle 410. In an embodiment (not illustrated), cap 420 may bethreaded into lower tubular section 440 of handle 410. For example,exterior threads 500 of cap 420 may thread into interior threads (notillustrated) in lower tubular section 440. In addition, cap 420 may alsoinclude features to secure handle 410 and ball joint assembly 30 onshaft 200. For example, cap 420 may be disposed over proximal end 430 ofshaft 200 with screw 520 inserted into threaded hole 510 of cap 420 toengage shaft 200. As illustrated, threaded hole 510 may be in head 480of cap 420. In an embodiment, elongated shaft 490 may have a rectangularshaped opening 505 into which square-shaped proximal end 430 of shaft200 may be inserted. It should be understood that other shaped openingsin elongated shaft 490 may also be suitable for use in embodiments ofthe present invention. With cap 420 secured onto shaft 200, handle 410may be rotated to, for example, tighten handle 410 down onto shaft 200,thus tightening handle 410 down onto ball joint assembly 30. Thepreceding description describes handle assembly 40 that can be used inaccordance with an embodiment of the present invention. However, itshould be understood that other suitable assemblies for tightening downonto ball joint assembly 30 can be used in accordance with embodimentsof the present invention.

Referring now to FIG. 10, ball joint 80 is illustrated in an unlockedposition in accordance with one embodiment of the present invention. Asillustrated, outer washers 330 may be located on either side of ball240. As previously described, ball 240 may be formed by upper portion260 and lower portion 270 that match together to form ball 240. In theillustrated embodiment, the uppermost of outer washers 330 is integralwith housing 250 with the lowermost of outer washers 330 slidablydisposed within housing 250. Inner washers 320 may also be located oneither side of ball 240. Outer shoulder 360 of each of inner washers 320should engage corresponding inner shoulder 380 of outer washers 330. Asillustrated, protruding rim 340 of each of inner washers 320 may extendthrough a corresponding one of outer washers 330. Rounded surface 350 ofprotruding rim 340 of each of inner washers 320 may contact ball 240. Aspreviously mentioned, rounded surface 350 may be smooth to allow forrotation of ball 240. As illustrated, springs 405 may be located oneither side of inner washers 320. In the illustrated embodiment, springs405 engage inner spring shoulder 370 of inner washers 320. In anembodiment, springs 405 may force outer shoulder 360 of each innerwasher 320 into engagement with inner shoulder 380 of each outer washer330.

Referring now to FIG. 11, ball joint 80 is illustrated in a lockedposition in accordance with one embodiment of the present invention.Ball joint 80 may be placed in a locked position to secure coupling rod220 in clamp 300 (illustrated on FIGS. 12-14). To place ball joint 80 ina locked position in accordance with one embodiment, handle assembly 40may be tightened down onto ball joint assembly 30, for example. As thehandle assembly 40 is tightened, inner washers 320 may be pushed insideof outer washers 330 so that protruding rim 340 no longer extendsthrough outer washers 330. The outer washers 330 may then engage ball240 with springs 405 forcing upper portion 260 and lower portion 270together. By forcing upper portion 260 and lower portion 270 together,clamp 300 may be closed onto a coupling rod 220 (illustrated on FIGS.12-14). In addition, engagement of outer washers 330 with ball 240 mayalso prevent rotation of ball 240. As previously mentioned, outerwashers 330 and/or outer surfaces 240 of ball 240 may be serrated. In anembodiment, inner serrated edge 390 of each outer washer 330 engagesserrated ball edges 285 to prevent rotation of ball 240. The precedingdescription describes one suitable technique for locking ball joint 80to prevent rotation of ball 240 and secure coupling rod 220 in clamp300. However, it should be understood that other suitable techniques forpreventing rotation of ball 240 and for securing coupling rod 220 inclamp 300 can be used in accordance with embodiments of the presentinvention.

One or more derotation apparatuses 10 may be used in the treatment ofspinal irregularities in accordance with embodiments of the presentinvention. For example, derotation apparatus 10 may be used to derotatea vertebral body, thus reducing rotation between vertebral bodies in apatient's spine. Derotation of the vertebral body with derotationapparatus 10 may also straighten curvature of the spine. In anembodiment, derotation apparatus 10 may be used in conjunction with animplant (e.g., a bone fastener coupled to a rod) to also addresscurvature of the spine. An embodiment of treating a spinal irregularitymay include coupling derotation apparatus 10 to an implant. In anembodiment, the implant may be attached to a vertebral body. Couplingderotation apparatus 10 to an implant may include, for example,placement of distal end 70 of inner sleeve 50 over implant. In anembodiment, distal end 70 may be placed over implant to preventseparation of inner sleeve from implant. Coupling derotation apparatus10 to implant further may include placing tube assembly 20 into a lockedposition to further secure inner sleeve 50 onto implant. In anembodiment, in the locked position, outer sleeve 60 may be disposed overdistal end 70 of inner sleeve 50, clamping distal end 70 onto theimplant. After securing the inner sleeve 50 on the implant, force may beapplied to handle assembly 40 to derotate the vertebral body to whichthe implant is attached.

Embodiments for treating a spinal irregularity further may includecoupling derotation apparatus 10 to at least one additional derotationapparatus 10 to form a coupled derotation system 225. For example, balljoints 80 in separate derotation apparatus 10 may be aligned so that acoupling rod 220 may be placed into a corresponding clamp 300 of thealigned ball joints 80. To lock the coupling rod 220 in place, thealigned ball joints 80 may then be placed in a locked position, forexample, by tightening of a corresponding handle assembly 40. It shouldbe understood that each derotation apparatus 10 in coupled derotationsystem 225 may be coupled to a corresponding implant. Force may beapplied to handle assembly 40 in at least one derotation apparatus 10 incoupled derotation system 225. In an embodiment, force may be applied tohandle assembly 40 of each derotation apparatus 10 in coupled derotationsystem 225. Application of force to handle assembly 40 should derotatethe vertebral bodies to which coupled derotation system 225 is attached.

Referring now to FIG. 12, coupled derotation system 225 for treatment ofspinal irregularities is illustrated in accordance with one embodimentof the present invention. As illustrated, coupled derotation system 225includes two derotation apparatuses 10 interconnected by coupling rod220. In the illustrated embodiment, derotation apparatuses 10 areconnected to bone fasteners 530 on either side of vertebral body 540.Rotational force applied to vertebral body 540 should be distributedbetween bone fasteners 530. As illustrated, bone fasteners 530 may be acomponent of a bone fixation system 550 for fusing spine 560 that mayinclude a single rod or a pair of parallel rods 570.

Referring now to FIG. 13, an embodiment of coupled derotation system 225for treatment of spinal irregularities is illustrated in which threederotation apparatuses 10 interconnected by coupling rod 220 areconnected to bone fasteners 530 on the same side of spine 560. In anembodiment, derotation apparatuses 10 may be connected to vertebralbodies 540 at the apex of the curvature of spine 560. This arrangementof derotation apparatuses 10 should distribute force across multiplelevels of spine 560.

Referring now to FIG. 14, an embodiment of coupled derotation system 225for treatment of spinal irregularities is illustrated in which multiplederotation apparatuses 10 are interconnected by coupling rods 220. Asillustrated, derotation apparatuses 10 may be coupled to bone fasteners530 over multiple levels of spine 560 and on both sides of spine 560.This arrangement of derotation apparatuses 10 should distribute forceacross multiple levels of spine 560 for derotation of vertebral bodies540.

FIG. 15 illustrates a derotation apparatus 10 in accordance withalternative embodiments of the present invention. As illustrated,derotation apparatus 10 includes a tube assembly 20, a ball jointassembly 30, and a handle assembly 40.

With reference to FIGS. 15-17, tube assembly 20 of derotation apparatus10 of FIG. 15 will be described in more detail in accordance withembodiments of the present invention. As illustrated, tube assembly 20may include an inner sleeve 50, an outer sleeve 60, and a locking handle600. In the illustrated embodiment, inner sleeve 50 has a distal end 70configured and adapted for attachment to an implant (not illustrated).Embodiments for attaching distal end 70 to the implant are described inmore detail above with respect to FIGS. 1-5. For example, distal end 70may be flexible so that distal end 70 can be pushed onto the head of abone fastening device (e.g., a pedicle screw). As best seen in FIG. 16,distal end 70 further may include features 610 on an inner surface 620of distal end 70 for allowing distal end 70 to slot onto the implant. Inthe illustrated embodiment, the features 610 are illustrated asprotruding from interior surface 620. Inner sleeve 50 further mayinclude at least one protruding surface 630, which may include beveledsurface 100, for example. In the illustrated embodiment, protrudingsurface 630 extends outward from exterior surface 640 of inner sleeve50. As illustrated, protruding surface 630 further may include raisedstop 650 on the surface thereof. Inner sleeve 50 further may includelongitudinally extending slots 660.

As illustrated by FIGS. 15 and 16, outer sleeve 60 may be disposed overinner sleeve 50 for locking inner sleeve 50 onto an implant. Outersleeve 60 may comprise one or more openings 670. These openings 670should provide access to inner sleeve 50, for example, so that interiorcomponents of the tube assembly 20 may be inspected and/or cleaned asdesired. In the illustrated embodiment, distal end 680 of outer sleeve60 includes one or more tabs 690 that extend longitudinally from outersleeve 60.

As previously mentioned, tube assembly 20 further may include lockinghandle 600. As illustrated by FIGS. 15-17, locking handle 600 may bedisposed on a proximal end 700 of inner sleeve 50. While notillustrated, locking handle 600 may be threadedly connected to proximalend 700 of inner sleeve 50, for example. The locking handle 600 may beconfigured to rotate and move down inner sleeve 50 placing the tubeassembly 20 in a locked position, thus coupling the derotation apparatus10 to an implant in accordance with embodiments of the presentinvention. As locking handle 600 is turned and moves down inner sleeve50, locking handle 600 should engage outer sleeve 60 causing outersleeve 60 to translate distally. As outer sleeve 60 translates distally,the tabs 690 of outer sleeve 60 should engage at least one protrudingsurface 630 on inner sleeve 50 such that distal end 70 of inner sleeve50 is pressed tighter against the implant (not illustrated), forexample. This tightening force should clamp distal end 70 onto theimplant preventing separation of distal end 70 from the implant.Accordingly, in this manner, derotation apparatus 10 can be securedlyconnected to an implant. Other suitable mechanisms for securingderotation apparatus 10 onto an implant may also be used in accordancewith embodiments of the present invention.

Derotation apparatus 10 of FIG. 15 further includes ball joint assembly30 in accordance with embodiments of the present invention. In general,ball joint assembly 30 should be configured and adapted to couplederotation apparatus 10 to at least one additional derotation apparatus10. With reference to FIGS. 15 and 18, ball joint assembly 30 includesone or more ball joints 80. Embodiments for operating ball joints 80 tosecure a rod 220 (e.g., FIG. 12) are described in more detail above withrespect to FIGS. 1, 2, and 6-11. As best seen by FIG. 18, ball jointassembly 30 further may include tube 710 below ball joints 80 with tube710 including reducing extension 720. As illustrated, reducing extension720 may have a reduced diameter as compared to tube 710. Reducingextension 720 further includes one or more raised surfaces 730projecting from exterior surface 740 of reducing extension 720. In theillustrated embodiment, reducing extension 720 includes two raisedsurfaces 730 on either side of reducing extension 720. In someembodiments, the raised surfaces 730 may extend longitudinally at leastpartially the length of reducing extension 720. As illustrated, each ofthe raised surfaces 730 include reducer tabs 750 that project beyonddistal end 760 of reducing extension 720. Reducing extension 710 may besized to fit in central bore 770 (e.g., FIG. 17) of inner sleeve 50.Raised surface 730 may be sized and configured to fit intolongitudinally extending slots 660 (e.g., FIG. 17) in inner sleeve 50 tokey the ball joint assembly 30 and sleeve assembly 20 so that thecomponents are properly oriented. Ball joint assembly 30 may be coupledto sleeve assembly 20. By way of example, ball joint assembly 30 may becoupled to sleeve assembly 20 by a threaded connection. While notillustrated, a portion of ball joint assembly 30, such as an exteriorsurface of tube 710, may have threads that engage corresponding threadsin proximal end 700 of inner sleeve 50. Threading the ball jointassembly 30 into sleeve assembly 20, for example, should distallytranslate reducer tabs 750. In accordance with present embodiments,distal translation of reducer tabs 750 can be used to reduce a rod 570(e.g., FIG. 12) into the head of a bone fastener 530 (e.g., FIG. 12),such as a screw, to which the sleeve assembly 20 is attached.

Derotation apparatus of FIG. 15 further includes handle assembly 40 inaccordance with embodiments of the present invention. Use of the handleassembly 40 to, for example, tighten the ball joints 80 onto a rod 220(e.g., FIG. 12) is described in more detail above with respect to FIG.1.

While the preceding description describes the use of one or more balljoints 80 (e.g., FIG. 1) in a derotation apparatus 10, it should beunderstood that ball joints 80 may be used for securing rods or othermembers (e.g., an artificial facet) to other medical devices. By way ofexample, one or more ball joints 80 may be used with an orthopedicfixation device 800, as described below with respect to FIGS. 19-20. Inone embodiment, orthopedic fixation device 800 is a pedicle screw.

FIG. 19 illustrates an orthopedic fixation device 800 comprising a bonefastener 810, an offset rod connection assembly 820, and a locking capassembly 830. In the illustrated embodiment, bone fastener 810 includeshead 815 and shaft 825. The illustrated embodiment shows shaft 825having threads 840. In some embodiments (not illustrated), shaft 825 mayhave a tapered shape. Those of ordinary skill in the art will appreciatethat shaft 825 may have a number of different features, such as threadpitch, shaft diameter to thread diameter, overall shaft shape, and thelike, depending, for example, on the particular application. Asillustrated, the shaft 825 extends downwardly from head 815. In certainembodiments, head 815 may have a tool engagement surface, for example,that can be engaged by a screw-driving tool or other device. The toolengagement surface can permit the physician to apply torsional or axialforces to bone fastener 810 to drive bone fastener 810 into bone, forexample. In the illustrated embodiment, the tool engagement surface ofhead 815 is a recess 835. For instance, recess 835 may be polygonal(e.g., hexagonal) for receiving a polygonal tool, such as an allenwrench, for example. The present invention is intended to encompass toolengagement surfaces having other shapes, such as slot or cross that maybe used, for example, with other types of screwdrivers. In analternative embodiment (not illustrated), the engagement surface may beconfigured with a protruding engagement surface that may engage with atool or device having a corresponding recess.

With additional reference to FIG. 20, offset rod connection assembly 820is configured to secure a rod 850 offset from longitudinal axis 860 oforthopedic fixation device 800 in accordance with embodiments of thepresent invention. Alternatively, the connection assembly 820 may beused to secure another member, such as an artificial facet, instead ofrod 850. Moreover, connection assembly 820 may be configured to rotatepolyaxially so that rod 850 can be placed in a desired position withrespect to shaft 810. In some embodiments, offset rod connectionassembly 820 may be a ball joint (e.g., ball joint 80 on FIG. 1).Embodiments of offset rod connection assembly 820 may operate to clamponto rod 850 in manner similar to that described previously for balljoint 80. For example, offset rod connection assembly 820 may berotatable about at least one axis and, preferably, at least two axes.For example, connection assembly 820 may be configured to rotate aboutat least one, or both, of the y-axis and z-axis. As illustrated, offsetconnection assembly 820 may comprise a ball 870 contained within housing875. In one embodiment, ball 870 is formed by upper portion 880 andlower portion 890 that when matched form ball 870. In an embodiment,upper portion 880 and lower portion 890 of ball 870 may each compriseserrated ball edges 900 on at least a portion of their respectiveexterior surfaces forming the outer surface of ball 870, as best seen onFIG. 20. In the illustrated embodiment, each of upper portion 880 andlower portion 890 comprises a tab, for example, upper tab 910 and lowertab 920, which may extend radially and outwardly from upper portion 880and lower portion 890, respectively. Together, upper tab 910 and lowertab 920 may be configured to form a clamp that grips rod 850. In thismanner, offset rod connection assembly 820 may retain rod 850 and secureit with respect to shaft 810.

Orthopedic fixation device 800 further may comprise locking cap assembly830 in some embodiments. In accordance with present embodiments,rotation of locking cap assembly 830 may be used to lock the offset rodconnection assembly 820, thus securing rod 850 and preventing furtherrotation of ball 870. For example, locking cap assembly 830 may berotated, thus moving the locking cap assembly 830 downward to forceupper portion 880 and lower portion 890 together. In this manner, uppertab 910 and lower tab 920 can be clamped onto rod 850 or an artificialfacet, for example. In addition, downward movement of locking capassembly 830 should also secure ball 870 from further rotation, thuslocking the angle of rod 850 with respect to shaft 810.

While it is apparent that the invention disclosed herein is wellcalculated to fulfill the objects stated above, it will be appreciatedthat numerous modifications and embodiments may be devised by thoseskilled in the art. Although individual embodiments are discussedherein, the invention covers all combinations of all those embodiments.

What is claimed is:
 1. An apparatus for treating a spinal irregularity:a first screw; a first and a second coupling rod; and a first derotationapparatus comprising: a tube assembly having a longitudinal axis andcomprising an inner sleeve and an outer sleeve disposed over the innersleeve, wherein the inner sleeve includes a distal end for attachment tothe first screw; a handle assembly; and a coupling rod engagementassembly disposed between the tube assembly and the handle assembly,wherein the coupling rod engagement assembly includes a first clamp forattaching to the first coupling rod and a second clamp for attaching tothe second coupling rod, wherein the first clamp is capable of rotatingwith respect to the longitudinal axis and is capable of rotating withrespect to an axis that is perpendicular to the longitudinal axis,wherein the second clamp is capable of rotating with respect to thelongitudinal axis and is capable of rotating with respect to an axisthat is perpendicular to the longitudinal axis, and wherein the firstclamp articulates independently of the second clamp.
 2. The apparatus ofclaim 1, wherein the outer sleeve is capable of sliding down onto adistal end of the inner sleeve to engage the inner sleeve and clamp adistal end of the first screw.
 3. The apparatus of claim 1, wherein thederotation apparatus comprises a locking mechanism capable of securingthe tube assembly on the first screw, the locking mechanism extendingradially from the inner sleeve and comprising a stop, an actuator, and aguide extending between the stop and the actuator.
 4. The apparatus ofclaim 3: wherein the outer sleeve comprises a first opening, a secondopening located closer to a proximal end of the outer sleeve than thefirst opening, and a channel connecting the first opening and the secondopening; wherein the locking mechanism is configured to extend through afirst opening in the outer sleeve with the stop engaging the outersleeve, when the tube assembly is in an unlocked position; and whereinthe locking mechanism is configured to extend through a second opening,with the stop engaging the outer sleeve, when the tube assembly is in alocked position.
 5. The apparatus of claim 1, wherein the coupling rodengagement assembly includes a first ball joint comprising an upperportion and a lower portion that match together to form a rotatableball, the upper portion comprising a radially extending upper tab, thelower portion comprising a radially extending lower tab, and the uppertab and the lower tab forming the first clamp for receiving the firstconnecting rod.
 6. The apparatus of claim 5, wherein the ball joint is aspring-loaded ball joint that comprises: an outer washer having aserrated surface, wherein the serrated surface is configured to preventrotation of the ball by engaging an outer surface of the ball when theball joint is in a locked position; and an inner washer fit within theouter washer and having a protruding rim with a smooth surface, andwherein the protruding rim is configured to extend through the outerwasher to engage smooth surface to extend through the outer washerengage an outer surface of the ball without preventing rotation of theball when the ball joint is in an unlocked position.
 7. The apparatus ofclaim 5, wherein the handle assembly comprises a handle, and wherein theclamp is configured to close down onto the coupling rod upon tighteningof the handle onto the ball joint assembly.
 8. The apparatus of claim 1,wherein the apparatus comprises: a second derotation apparatuscomprising: a second tube assembly comprising an inner sleeve and anouter sleeve disposed over the inner sleeve, wherein the inner sleevehas a distal end for attachment to a second screw; a second handleassembly; and a second coupling rod engagement assembly disposed betweenthe tube assembly and the handle assembly, wherein the coupling rodengagement assembly includes a third clamp for attaching to the firstcoupling rod and a fourth clamp for attaching to the second couplingrod.
 9. The apparatus of claim 8, wherein the apparatus comprises: athird derotation apparatus comprising: a third tube assembly comprisingan inner sleeve and an outer sleeve disposed over the inner sleeve,wherein the inner sleeve has a distal end for attachment to a thirdscrew; a third handle assembly; and a third coupling rod engagementassembly disposed between the tube assembly and the handle assembly,wherein the coupling rod engagement assembly includes a fifth clamp forattaching to the first coupling rod and a sixth clamp for attaching tothe second coupling rod.
 10. A method for treating a spinalirregularity: providing a first derotation apparatus comprising: a tubeassembly comprising an inner sleeve and an outer sleeve disposed overthe inner sleeve, a handle assembly; and a coupling rod engagementassembly disposed between the tube assembly and the handle assembly,wherein the coupling rod engagement assembly includes a first clamp anda second clamp, wherein the first clamp is capable of rotating withrespect to the longitudinal axis and is capable of rotating with respectto an axis that is perpendicular to the longitudinal axis, wherein thesecond clamp is capable of rotating with respect to the longitudinalaxis and is capable of rotating with respect to an axis that isperpendicular to the longitudinal axis, and rotating the first clamp toalign with and engage a first coupling rod; rotating the second clamp toalign with and engage a second coupling rod; sliding the outer sleeve ofthe first derotation apparatus downward over the inner sleeve to clamp adistal end of the inner sleeve onto the head of a first screw.
 11. Amethod for treating a spinal irregularity: providing a first derotationapparatus comprising a first coupling rod engagement assembly; providinga second derotation apparatus comprising a second coupling rodengagement assembly; coupling the first derotation apparatus to a firstscrew, the first screw is coupled to a vertebral body; coupling thesecond derotation apparatus to a second screw, the second screw iscoupled to a vertebral body; aligning the first coupling rod engagementassembly of the first derotation apparatus and the second coupling rodengagement assembly of the second derotation apparatus; and coupling acoupling rod between the first coupling rod engagement assembly of thefirst derotation apparatus and the second coupling rod engagementassembly of the second derotation apparatus to interconnect the firstderotation apparatus and the second derotation apparatus.
 12. The methodof claim 11, wherein the first screw and the second screw are secured oneither side of the same vertebral body.
 13. The method of claim 11,wherein the first screw and the second screw are secured on the sameside of the spine.
 14. The method of claim 11, further comprising:providing a third derotation tube comprising a third coupling rodengagement assembly; and coupling the coupling rod to the third couplingrod engagement assembly to interconnect the first derotation apparatus,the second derotation apparatus, and the third derotation apparatus. 15.The method of claim 11, wherein the first derotation apparatus furthercomprises a third coupling rod engagement assembly and the secondderotation apparatus further comprises a fourth coupling rod engagementassembly.
 16. The method of claim 15 further comprising: aligning thethird coupling rod engagement assembly of the first derotation apparatusand the fourth coupling rod engagement assembly of the second derotationapparatus; and coupling a second coupling rod between the third couplingrod engagement assembly of the first derotation apparatus and the fourthcoupling rod engagement assembly of the second derotation apparatus tointerconnect the first derotation apparatus and the second derotationapparatus.
 17. The method of claim 11, wherein the first derotationapparatus further comprises an inner sleeve and an outer sleeve and thesecond derotation apparatus further comprises an inner sleeve and anouter sleeve.
 18. The method of claim 17 further comprising sliding theouter sleeve of the first derotation apparatus downward over the innersleeve to clamp a distal end of the inner sleeve onto the head of afirst screw.
 19. The method of claim 18 further comprising sliding theouter sleeve of the second derotation apparatus downward over the innersleeve to clamp a distal end of the inner sleeve onto the head of asecond screw.